Examples: DPI: Portable DPI related helpers in the _Win32 examples. Using one in examples's main.cpp, the GetDpiScale functions are not wired anywhere for now. (#1542, #1676)

Viewport: Changed signature of ResizeViewport to be consistent with other similar functions.

Viewport: Coupling non-main viewport to one window. Viewport name derived from the window. Added ImGuiConfigFlags_PlatformNoTaskBar, off by default (aka re-established task-bars by default for now). (#1542)

Viewport: Reorganized viewport enable flags. Both user + platform + renderer need to enable a flag. (#1542)

Renamed ImGuiNavFlags io.NavFlags to ImGuiConfigFlags io.ConfigFlags. (#787)

Examples: DX11 + Win32: Initial attempt at implementing the viewport/platform api. (WIP/test API) (#1542)

Examples: Titles/comments in headers

Merge branch 'master' into examples_refactor

Examples: WIn32: Prefixing every Win32 function calls with :: to denote global namespace in a consistent manner.

Examples: DirectX9: Reusing imgui_impl_win32, removed that code from imgui_impl_dx9

Examples: DirectX11: Extracted imgui_impl_dx11.* instead imgui_impl_dx11 and imgui_impl_win32